1. Field
The field includes methods of making bipolar devices using electrical potentials and electric fields, and in particular methods of making bipolar electrochemical devices, such as batteries, using electrophoresis.
2. Summary of the Related Art
Batteries, and particularly rechargeable batteries, are widely used in a variety of devices such as cellular telephones, laptop computers, personal digital assistants, and toys. Manufacturing constraints generally limit the available shapes of batteries, with common form factors including cylinders, button cells (thin discs), and prismatic forms. The energy density of such batteries is relatively low, due to poor volumetric utilization of space within the electrochemical devices. Recently “three-dimensional batteries” have been proposed, which have anodes and cathodes with active surface areas exposed in three dimensions, and potentially exhibit improved performance results compared to standard battery geometries. A need exists for new manufacturing methods to create electrochemical devices with improved energy density, power density, and cycle life, as well as reduced manufacturing cost.
Electrophoresis, the motion of charged particles under an applied electric field, is used to characterize the behavior of solutions and suspensions, and has also been used to deposit materials in the form of thin films, coatings, and even bulk products. The formation of battery electrodes by electrophoretic deposition has been disclosed (e.g., Kanamura et al., Electrochemical and Solid-State Letters, 3:259-262 (2000)). Typically, a coating is electrophoretically deposited on a metal substrate from a suspension of particles in a liquid. The deposited coating is then removed from the apparatus or bath in which the deposition was carried out, and subsequently used for a desired application. For example, to prepare a battery, an electrophoretically-deposited electrode is removed from its liquid deposition bath, dried, and used as a component in a device assembly. However, the act of electrophoresis does not by itself create a complete device.